The earliest fossil evidence for landplants comes from spores: covered by sporopollenin, a complex molecule resistant to chemical and physical degradation they may be found in various and old sediments.

Wellman et al. (2003) presented spores from Oman, as liverworts spores dated from Mid-Ordovician.

Cryptospores from the upper part of the Zanjón Formation. (a) Distal face of Chomotriletes? sp. (b) Proximal face of Chomotriletes? sp. (c,d) Gneudnaspora (Laevolancis) divellomedia or Laevolancis chibrikova . (e,f) Sphaerasacus glabellus. (g) Tetrahedraletes cf. medinensis. (h) New genus. Scale bars, 20 µm. From Rubinstein, C. V., Gerrienne, P., de la Puente, G. S., Astini, R. A. and Steemans, P. (2010), Early Middle Ordovician evidence for land plants in Argentina (eastern Gondwana). New Phytologist, 188: 365–369. doi:10.1111/j.1469-8137.2010.03433.x